A vast upsurge in the use of a deadly toxin to smooth out facial wrinkles concerns a leading doctor - who says its long-term safety is unproven.

Dr Peter Misra, from the National Hospital for Neurology and Neurosurgery, says that while immediate adverse reactions to Botox are rare, evidence for the long-term effects of the treatment has not yet been gathered.

It is easy to forget that it is a potent neurotoxin and that its very long-term effects are still unknown

Dr Peter Misra, National Hospital for Neurology and Neurosurgery

Writing in the British Medical Journal, he said: "In this atmosphere of 'Botox parties' - where champagne-sipping socialites are injected with botulinum toxin - it is easy to forget that it is a potent neurotoxin and that its very long-term effects are still unknown."

Botox is actually made out of the poison which can make botulism such a lethal infection.

A serious botulism infection is dangerous because the toxin paralyses vital muscles needed for breathing.

However, Botox treatments involve a far smaller dose of the drug which has a similar effect, but only on a tiny area of muscle near to the injection site.

It has been used for some time to help reduce the symptoms of some forms of spasticity by correcting imbalances and spasms in muscles to improve gait and posture.

Party drug

In recent years, however, this effect has been harnessed by the cosmetic surgery industry.

Botox is more popular than ever

If a tiny amount of the toxin is injected into certain areas of the face, it creates the effect of stretching out the muscles near the site of wrinkles or crow's feet, reducing their appearance.

Of course, the patient will be unable to move these particular muscles voluntarily.

The treatment effect lasts for a few months.

Botox is currently used in over 70 countries, and there has been no evidence to date of any long-term safety concerns associated with the treatment

Spokesman, Allergan UK

Revenue for the global sales of Botox has increased from $25m in 1993 to $310m in 2001, mainly on the back of cosmetic use.

It remains unlicensed for this use in the UK - meaning that doctors are free to use it, but must be personally responsible for any ill-effects.

A spokesman for Allergan, which manufactures Botox, said that the treatment had more than 13 years of successful clinical use in a variety of conditions.

She said: "Botox is currently used in over 70 countries, and there has been no evidence to date of any long-term safety concerns associated with the treatment.

"As with any pharmaceutical medical product, there are potential side-effects.

"Side-effects that can occur are known to be minor and of temporary nature."